Priming by airborne signals boosts direct and indirect resistance in maize

Authors

  • Jurriaan Ton,

    Corresponding author
    1. Laboratory of Evolutionary Entomology, Institute of Zoology, University of Neuchâtel, Neuchâtel, Switzerland,
    2. Institute of Environmental Biology, Phytopathology, Utrecht University, Utrecht, The Netherlands,
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  • Marco D'Alessandro,

    1. Laboratory of Evolutionary Entomology, Institute of Zoology, University of Neuchâtel, Neuchâtel, Switzerland,
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  • Violaine Jourdie,

    1. Laboratory of Evolutionary Entomology, Institute of Zoology, University of Neuchâtel, Neuchâtel, Switzerland,
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  • Gabor Jakab,

    1. Biochemistry and Molecular Biology, Institute of Botany, University of Neuchâtel, Neuchâtel, Switzerland, and
    2. Plant Physiology, Faculty of Sciences, University of Pécs, Pécs, Hungary
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  • Danielle Karlen,

    1. Laboratory of Evolutionary Entomology, Institute of Zoology, University of Neuchâtel, Neuchâtel, Switzerland,
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  • Matthias Held,

    1. Laboratory of Evolutionary Entomology, Institute of Zoology, University of Neuchâtel, Neuchâtel, Switzerland,
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  • Brigitte Mauch-Mani,

    1. Biochemistry and Molecular Biology, Institute of Botany, University of Neuchâtel, Neuchâtel, Switzerland, and
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  • Ted C.J. Turlings

    1. Laboratory of Evolutionary Entomology, Institute of Zoology, University of Neuchâtel, Neuchâtel, Switzerland,
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(fax +31 30 2518366; e-mail j.ton@bio.uu.nl).

Summary

Plants counteract attack by herbivorous insects using a variety of inducible defence mechanisms. The production of toxic proteins and metabolites that instantly affect the herbivore's development are examples of direct induced defence. In addition, plants may release mixtures of volatile organic compounds (VOCs) that indirectly protect the plant by attracting natural enemies of the herbivore. Recent studies suggest that these VOCs can also prime nearby plants for enhanced induction of defence upon future insect attack. However, evidence that this defence priming causes reduced vulnerability to insects is sparse. Here we present molecular, chemical and behavioural evidence that VOC-induced priming leads to improved direct and indirect resistance in maize. A differential hybridization screen for inducible genes upon attack by Spodoptera littoralis caterpillars identified 10 defence-related genes that are responsive to wounding, jasmonic acid (JA), or caterpillar regurgitant. Exposure to VOCs from caterpillar-infested plants did not activate these genes directly, but primed a subset of them for earlier and/or stronger induction upon subsequent defence elicitation. This priming for defence-related gene expression correlated with reduced caterpillar feeding and development. Furthermore, exposure to caterpillar-induced VOCs primed for enhanced emissions of aromatic and terpenoid compounds. At the peak of this VOC emission, primed plants were significantly more attractive to parasitic Cotesia marginiventris waSPS. This study shows that VOC-induced priming targets a specific subset of JA-inducible genes, and links these responses at the molecular level to enhanced levels of direct and indirect resistance against insect attack.

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